In general, inkjet printing machines or printers include at least one printhead unit that ejects drops or jets of liquid ink onto an image receiving surface such as an image substrate. A phase change inkjet printer employs phase change inks that are in the solid phase at ambient temperature, but transition to a liquid phase at an elevated temperature. The melted ink can then be ejected as drops or jets by a printhead assembly onto a heated image substrate. In some printers, the image receiving surface is a recording media, in which case the ink is ejected directly onto the image substrate. In other printers, the image receiving surface is an intermediate transfer surface onto which ink is ejected and subsequently transferred to a recording media.
One issue faced in inkjet printing technology is controlling the gloss level of all or parts of an image, page, or print job. Gloss is a measure of the reflective properties of a surface. High gloss indicates that the surface reflections are mirror-like or specular, which means the angle of reflection closely matches the angle of incidence of light illuminating the surface. Low gloss indicates that the surface produces diffuse reflections where incident light is scattered over a broad range of angles during reflection. Gloss levels may be influenced by both the type of colorant as well as the type of media used to form a printed image. Controlling gloss levels of a printed image may be difficult because ejected ink has a gloss level that differs from the gloss level exhibited by unprinted media. In addition, variations in the density of the ink ejected onto the media to form an image may cause corresponding variations in the gloss level of the image. These variations in gloss levels across a printed image may not be acceptable to consumers.
One method that has been used to control gloss levels of printed images is to coat the entire printed media with a colorless coating material that is designed to provide a protective layer on the printed media as well as to provide a substantially uniform gloss to the printed media. There are many types of coating materials that may be used. For example, coating inks have been developed that are capable of being jetted using standard printheads. The composition of these coating inks can be adjusted to provide substantially any level of gloss to a printed image such as high gloss, matte, satin, etc.
In some cases, consumers may desire to be able to select and print specific gloss levels to all or part of a printed image, page or print job. The various gloss levels, e.g., high gloss, semi-gloss, matte, etc., may each have characteristics that are desired for various printing applications. For example, color images having a high gloss level may have more vibrant colors than color images having a lower gloss level. Similarly, printed text having a low gloss level may be easier to read than printed text having a high gloss level. By selectively varying the gloss level across the printed media, different areas of the printed media may be enhanced and/or contrasted to produce aesthetically striking results.
Most previously known printers, however, are capable of providing only a single gloss finish to printed images, e.g., a high gloss finish. Some printers have been developed that are capable of providing multiple gloss finishes to printed images. In order to provide the multiple gloss levels in these systems, however, a separate coating ink is typically provided for each desired gloss level. Because coating inks having different gloss levels are typically manufactured at an off-site location, supplies of each desired gloss coating ink may have to be ordered well in advance of their actual use. In addition, customers may be required to order quantities of the different gloss inks from the supplier greater than they need.